1. Field of the Invention
The present invention relates to a radar apparatus that performs signal processing on a digital basis and, more particularly, to a radar apparatus of a digital beamforming (DBF) type provided with an array antenna consisting of a plurality of antenna elements to form antenna beams by digital processing.
2. Related Background Art
An example of the radar apparatus of the DBF type is the one described in Japanese Laid-open Patent Application No. 6-88869. In this conventional radar apparatus, an RF amplifier, a mixer, a filter, and an A/D converter are connected to each of the antenna elements forming the array antenna and digital signals outputted from the respective A/D converters are taken into a digital beamforming processor to be subjected to a digital beamforming process.
In general, the radar apparatus uses high-frequency electromagnetic waves such as microwaves or millimeter waves, and analog devices (such as the RF amplifiers and mixers) operating at such high frequencies are very expensive.
The conventional radar apparatus described above needs a lot of analog devices, because these analog devices are provided for each of the antenna elements. Therefore, high production cost is unavoidable. Particularly, a means for improving performance can be increase in the number of antenna elements, but the increase of the antenna elements will result in increasing the number of high-frequency analog devices attendant thereon and in turn increasing the cost. This was the hindrance against the increase in the number of antenna elements. The increase in the number of analog devices will also result in increasing the scale of the radar apparatus.